This invention relates to antibodies specific to tofacitinib, which are useful, e.g., in assay methods and assay kits for monitoring blood levels of the drug.
Tofacitinib is a potent immunosuppressant in development for the treatment of rheumatoid arthritis (RA), psoriasis, inflammatory bowel disease, and other immunological diseases, as well as for the prevention of organ transplant rejection. Tofacitinib specifically inhibits Janus activated kinase 3 (JAK3), which has a pivotal role in cytokine signal transduction governing lymphocyte survival, proliferation, differentiation and apoptosis.
In certain circumstances, when organs such as kidney, heart, lung, bone marrow, and liver are transplanted in humans, the body will sometimes reject the transplanted tissue. One treatment of organ transplant rejection comprises suppression of the immune system in a controlled manner with immunosuppressant drugs such as tofacitinib. Immunosuppressant drugs are carefully administered to transplant recipients to prevent rejection of the foreign (i.e. non-self) tissue. Successful treatment with immunosuppressant drugs requires the measurement of drug concentrations, followed by subsequent dosage adjustments to maximize efficacy while minimizing toxicity. Monitoring blood levels of tofacitinib in patients treated with tofacitinib is thus very desirable in order to regulate the dosage. The appropriate dosage will maintain the minimum drug activity level sufficient for pharmacologic activity while avoiding any undue risk of side effects. Thus, need exists for a sensitive and reliable assay for measuring tofacitinib levels in patients that can be performed quickly and easily in a clinical setting as part of the development of tofacitinib as a pharmaceutical.
To support the use of tofacitinib in the clinical setting, particularly for use in the prevention of organ transplant rejection, a long-felt need exists for monitoring plasma levels of tofacitinib in many patients to ensure that therapeutic levels are maintained, as well as to guide adjustment of dosages in a timely fashion as needed. This activity is often referred to as Therapeutic Drug Monitoring (TDM). TDM plays a key role in helping clinicians maintain blood and plasma levels of immunosuppressive drugs within their respective therapeutic ranges. Variation in concentrations outside of the narrow therapeutic ranges may result in adverse clinical outcomes. TDM ensures that concentrations of drug are not too high or too low, thereby reducing the risks of toxicity or rejection, respectively. Therapeutic monitoring of immunosuppressive drugs has generally been based on several choices of assay and biologic fluid (i.e., whole blood, plasma) appropriate for a particular drug.
A reliable liquid chromatography-mass spectrometry (LC-MS/MS) based assay is available for monitoring therapeutic levels of tofacitinib. Unfortunately, most clinical sites around the country and around the world are not set up to routinely perform LC-MS/MS assays in house. Clinical sites typically prefer relatively rapid, inexpensive, and easy to perform assays to streamline their TDM efforts. Accordingly, it would be advantageous to have immunoassays configured to detect tofacitinib in a patient's blood, serum, plasma, and/or other biological fluids or samples. Additionally, it would be advantageous to have tofacitinib-based immunogens for use in producing anti-tofacitinib antibodies.
Further, it would be advantageous to have specific anti-tofacitinib antibodies that bind tofacitinib but do not substantially bind at least one metabolite of tofacitinib. Such antibodies would be useful, among other things, to detect clinically relevant concentrations of tofacitinib in a sample from a patient undergoing therapy wherein tofacitinib is administered to the patient.
There have been no previous reports of monoclonal antibodies which recognize tofacitinib. There are inherent difficulties in making monoclonal antibodies to tofacitinib because tofacitinib is not immunogenic and is itself immunosuppressive. Moreover, as the metabolites of tofacitinib have not been well characterized in the literature, it is difficult to identify a monoclonal antibody capable of differentiating between tofacitinib and its metabolites. A need exists for an accurate assay to detect active tofacitinib but not its inactive metabolites. The present invention meets that need.